Since recent experiments suggest an important nonvagal mechanism in insulin choleresis, it seems important to determine more precisely insulin's role in regulating bile formation. It is proposed to investigate whether insulin acts directly on the liver to stimulate bile flow by observing the action of that peptide on the isolated perfused rat liver. Because insulin from the islets of Langerhans is released into portal venous blood it is also of interest to compare the choleretic action of insulin given either into the portal system or into a systemic vein. To investigate whether endogenous insulin may participate in the choleretic response to a meal it is proposed to study feeding choleresis in dogs before and after destruction of the Beta cells with streptozotocin.